1. Field of the Invention
The present invention relates to a liquid ejection head, and more particularly, to pressure determination technology for a liquid ejection head which ejects liquid onto an ejection receiving medium.
2. Description of the Related Art
An inkjet recording apparatus having an inkjet type of print head forms a desired image on a medium by ejecting ink from a plurality of nozzles provided in the print head. In an inkjet recording apparatus of this kind, it is possible to judge the state of the pressure chambers and nozzles on the basis of a determination signal obtained by determining the pressure in the pressure chambers which accommodate the ink that is ejected from the respective nozzles. For example, if the frequency of the determined pressure (pressure wave) is lower than the resonance frequency of the pressure chamber, then it can be judged that an air bubble has occurred inside the pressure chamber, and that an ejection abnormality has arisen in the nozzle which ejects the ink accommodated in that pressure chamber.
In the ink spraying apparatus described in Japanese Patent Application Publication No. 6-155733, a drive pulse is applied to a piezo element by a drive device, thereby causing the piezo element to deform a plurality of times, and hence the ink inside an ink chamber is gradually sprayed and forms into one ink droplet. A determination device determines the variation in the ink inside the ink chamber after each prescribed number of pulses of the drive pulse, and a subsequent pulse is generated on the basis of the determination result, in such a manner that the pulse interval between a plurality of pulse driving actions is adjusted to achieve an optimal driving state.
Furthermore, in the piezoelectric liquid droplet spraying apparatus described in Japanese Patent Application Publication No. 7-132592, a drive pulse for measurement is applied to a piezo element prior to a printing operation, the pressure variation in the pressure chamber is determined by means of the piezo element and a determination circuit, and the drive waveform is calculated on the basis of the characteristics of the pressure variation.
In the inkjet recording head and inkjet recording apparatus described in Japanese Patent Application Publication No. 2000-301714, a flexible film is provided on at least one surface of an ink reservoir, and the flexible film contains drive elements comprising a piezoelectric material layer and a pair of electrodes. Therefore, pressure changes in the reservoir can be absorbed effectively.
However, since the signals obtained from pressure sensors often have a very weak current or a very weak voltage and pulse noise is often superimposed on the determination signals, then it may be impossible to determine the pressure accurately due to the effects of the noise on the determination signal. In particular, if the pressure sensor does not have suitable characteristics (frequency characteristics), then the S/N ratio will be high and will have a great affect on the determination signal.
In the ink spraying apparatus defined in Japanese Patent Application Publication No. 6-155733, the piezoelectric liquid droplet spraying apparatus described in Japanese Patent Application Publication No. 7-132592 and the inkjet recording head and inkjet recording apparatus described in Japanese Patent Application Publication No. 2000-301714, there is no disclosure regarding specific solutions for improving determination accuracy.